[Xen-devel] [PATCH V2] libxl: don't add cache mode for qdisk cdrom drives

[Jim Fehlig <jfehlig@xxxxxxxx>]

qemu commit 91a097e7 forbids specifying cache mode for empty
drives. Attempting to create a domain with an empty qdisk cdrom
drive results in

qemu-system-x86_64: -drive if=ide,index=1,readonly=on,media=cdrom,
   cache=writeback,id=ide-832: Must specify either driver or file

libxl only allows an empty 'target=' for cdroms. By default, cdroms
are readonly (see the 'access' parameter in xl-disk-configuration.txt)
and forced to readonly by any tools (e.g. xl) using libxlutil's
xlu_disk_parse() function. With cdroms always marked readonly,
explicitly specifying the cache mode for cdrom drives can be dropped.
The drive's 'readonly=on' option can also be set unconditionally.

Signed-off-by: Jim Fehlig <jfehlig@xxxxxxxx>
---

V2:
Drop explicitly setting cache mode since cdrom devices are
readonly.
Unconditionally add 'readonly=on' drive option for cdroms.

 tools/libxl/libxl_dm.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index fd12844..959e292 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -1368,8 +1368,8 @@ static int libxl__build_device_model_args_new(libxl__gc 
*gc,
 
             if (disks[i].is_cdrom) {
                 drive = libxl__sprintf(gc,
-                         
"if=ide,index=%d,readonly=%s,media=cdrom,cache=writeback,id=ide-%i",
-                         disk, disks[i].readwrite ? "off" : "on", dev_number);
+                         "if=ide,index=%d,readonly=on,media=cdrom,id=ide-%i",
+                         disk, dev_number);
 
                 if (target_path)
                     drive = libxl__sprintf(gc, "%s,file=%s,format=%s",
-- 
1.8.0.1


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